1. Field of the Invention
The present invention relates to a system for forcefully igniting sprayed fuel of a diesel engine, more particularly, to an ignition system for starting a diesel engine with an engine starter motor by forcefully burning sprayed fuel oil, at least until the sprayed fuel becomes spontaneously ignitable.
2. Description of the Prior Art
In a diesel engine, particularly in a diesel engine of the type having subcombustion chambers such as a swirl chambers or a precombustion chambers, each glow plug is provided within a corresponding subcombustion chamber. The glow plugs act as means for heating the subcombustion chambers before the engine starter motor is actuated so as to ignite a spray of fuel oil injected and mixed with compressed air in the subcombustion chambers. The glow plugs start the diesel engine in conjunction with the starter motor by igniting a spray of fuel injected through a fuel injection valve. The injected fuel is brought into contact with the surface of the corresponding glow plug which is heated by heavy current flowing therethrough. When the engine needs to be started at a low ambient temperature, e.g., at an air temperature of minus 25.degree. C., each glow plug requires a continuous heavy current of about 8 amperes (12V.times.8A) for 30 to 60 seconds before the diesel engine can be started by means of the engine starter motor so as to activate the engine into a spontaneous fuel ignition state.
In this way, the conventional auxiliary engine starting system for a diesel engine requires a preheating operation in which a large current is sent through each glow plug before the engine starter motor is actuated.
Therefore, the engine starting procedure is complicated and it takes a long time for the engine to reach in the spontaneous fuel ignition state. In addition, a great quantity of electrical power is consumed in order to heat the glow plugs so that the load on the DC power supply (battery) is increased and accordingly fuel consumption is increased. On the other hand, if the ignition operation stops immediately after the engine enters in the spontaneous ignition state, the engine will not revolve smoothly so that irregular vibrations may occur.